The information that parents give us through questionnaires is indispensable for many of our projects. For example, to get a better picture of how children behave in everyday life, we ask parents to fill out questionnaires. The questions are often about how your child reacts in certain situations, but can also be about sleeping, crying and your child’s health. Also, we often ask parents to complete questionnaires about themselves. Both during pregnancy and also during the first years of the child's life, we are interested in the emotional and physical well-being of the parents, but also in their (caregiving) activities, sleep, and health. The questionnaire you are asked to fill in will depend on the specific study that you participate in.